1. Field of the Invention
The present invention relates to a process for isomerization of .beta.-.gamma.-unsaturated alcohol or its ester. More particularly, it relates to a process for cis-trans isomerization of a .beta.-.gamma.-unsaturated alcohol or its ester especially from a cis-form to a trans-form .beta.-.gamma.-unsaturated alcohol or its ester.
2. Description of the Prior Art
It has been known to carry out a cis-trans isomerization of .beta.-.gamma.-unsaturated alcohol in the presence of an acidic catalyst (Japanese Patent Publication 8107/1963) and in the presence of a transition metal type catalyst (Japanese Unexamined Patent Publication 2940/1976).
There is no prior art for a cis-trans isomerization of .beta.-.gamma.-unsaturated ester.
In the conventional cis-trans isomerization of .beta.-.gamma.-unsaturated alcohol, expensive reagent is required or a preparation of the catalyst is complicate or a separation and reuse of the catalyst is not easy. These processes are disadvantageous in an industrial process. It has disadvantages of a shift of the double bond or a shift of hydroxy group in the isomerization even though it can be employed as an industrial process. It has been difficult to attain the selective cis-trans isomerization even though it can be employed as an industrial process. When an acidic catalyst or an alkaline catalyst is used for the isomerization of .beta.-.gamma.-unsaturated ester, a shift of the double bond is performed to be difficult to attain the selective cis-trans isomerization.
The inventors have studied cis-trans isomerizations of .beta.-.gamma.-unsaturated alcohols or its esters to overcome the difficulties.